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Orangefs wins when it can do IO on large (up to four meg) blocks at a time, and looses when it has to do tiny "small io" reads and writes. Accessing Orangefs through the pagecache with the kernel module helps with small io, both reading and writing, a great deal. Readpage generally tries to fetch a page (four k) at a time. We'll let users use "count" (as in read(2) or pread(2) for example) as a knob to control how much data they get from Orangefs at a time and we'll try to use the data to fill extra pagecache pages when we get to ->readpage, hopefully resulting in fewer calls to readpage and Orangefs userspace. We need a way to remember how they set count so that we can still have it available when we get to ->readpage. - We'll use file->private_data to keep track of "count". We'll wrap generic_file_open with orangefs_file_open and initialize private_data to NULL there. - In ->read_iter we have access to both "count" and file, so we'll kmalloc some space onto file->private_data and store "count" there. - We'll kfree file->private_data each time we visit ->flush and reinitialize it to NULL. Signed-off-by: Mike Marshall <hubcap@omnibond.com> Signed-off-by: Martin Brandenburg <martin@omnibond.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.